This invention relates generally to the field of turbochargers and, more particularly, to a system for controlling electric assisted turbochargers.
Turbochargers for gasoline and diesel internal combustion engines are devices known in the art that are used for pressurizing or boosting an intake air stream, routed to a combustion chamber of the engine, by using the heat and volumetric flow of exhaust gas exiting the engine. Specifically, the exhaust gas exiting the engine is routed into a turbine housing of a turbocharger in a manner that causes an exhaust gas-driven turbine to spin within the housing. The exhaust gas-driven turbine is mounted onto one end of a shaft that is common to a radial air compressor mounted onto an opposite end of that shaft. Thus, rotary action of the turbine also causes the air compressor to spin within a compressor housing of the turbocharger that is separate from the exhaust housing. The spinning action of the air compressor causes intake air to enter the compressor housing and be pressurized or boosted a desired amount before it is mixed with fuel and combusted within the engine combustion chamber.
Because the rotary action of the turbine is dependent upon the heat and volumetric flow of exhaust gas exiting the engine, turbochargers are often of reduced effectiveness when the engine to which they are coupled is run at a low speed. The reduced effectiveness is often labeled turbo-lag. In order to overcome turbo-lag when the heat and volumetric flow of exhaust gas is low, an electric motor is known for rotating the shaft and inducing the compressor to spin.
Without proper timing and power provision to the electric motor, the electric motor can hinder rather than enhance the performance of the turbocharger. It is, therefore, desirable to provide intelligent operation control to the electric motor in order to both maximize engine performance, and to provide a responsible electric power management system. It is desired that such intelligent operation control system be configured to prevent powering the electric motor of the electric assisted turbocharger during engine operating conditions not calling for turbocharger assistance.
Additionally, engine designers constantly seek improvements for controlling boost pressure on an engine. In an effort to more rapidly and more precisely control boost pressure, in a conventional turbocharger, designers have replaced pneumatic actuators with electronic controlled actuators for moving wastegate valves and variable geometry blades. The electronic actuators receive their instructions from the engine electronic control unit (ECU) and various engine sensors. This results in a reduction in time to reach a target boost pressure, and smaller over-boost and under-boost error margins.
It is, therefore, also desirable that an intelligent operation control system for use with an electric assisted turbocharger be configured to reduce the time needed to reach a target boost pressure, and to reduce over-boost and under-boost error margins, thereby enabling an improved degree of turbocharger efficiency.
A system for controlling an electric assisted turbocharger, constructed according to principles of this invention, employ an electric motor that is disposed within a turbocharger, an electric motor controller is electrically coupled to the electric motor for purposes of controlling the same, and a memory means is electrically coupled to the electric motor controller. The memory means is configured having a condition map that correlates electric motor instructions with engine and turbocharger conditions. The system includes a number of sensors that are electrically coupled to the electric motor controller. The sensors are configured to sense conditions of at least one of the turbocharger and the internal combustion engine that is coupled thereto.
The electric motor controller is configured to control the electric motor based upon the input received from the plurality of sensors as compared to the data contained in the multi-dimensional condition map. In an example invention embodiment, the motor controller is configured to operate the electric motor of the electric assisted turbocharger in a manner best suited to provide the desired engine performance. For example, the system may comprise a clutch engagement sensor, that senses whether a clutch is engaged, and or a brake engagement sensor, that senses whether a brake is engaged, and the electric motor controller is configured to remove power to the electric motor when the clutch engagement sensor and/or the brake sensor indicates that the clutch is not engaged or the brake is activated.
In another invention embodiment, the system comprises a boost pressure sensor that senses the boost pressure in the turbocharger and that is configured to achieve a target boost pressure, and to reduce over-boost and under-boost error margins. In such embodiment, the electric motor controller is configured to select a target boost pressure based upon application of the sensed conditions of at least one of the turbocharger and the internal combustion engine to the condition map in the memory. The system is configured to supply increased power to the electric motor when the boost pressure sensed by the boost pressure sensor is lower than the selected target boost pressure, and to supply decreased power to the electric motor when the boost pressure sensed by the boost pressure sensor is higher than the selected target boost pressure. Additionally, the system can be configured to operate in a generator mode, whereby the electrical motor is operated to produce electricity based on the spinning of the turbine by the exhaust gas.